Role of Extracellular Vesicles in Immunity and Host Defense

Abstract

Extracellular vesicles (EVs) are membrane-bound structures released by cells and have become significant players in immune system functioning, primarily by facilitating cell-to-cell communication. Immune cells like neutrophils and dendritic cells release EVs containing bioactive molecules that modulate chemotaxis, activate immune cells, and induce inflammation. EVs also contribute to antigen presentation, lymphocyte activation, and immune tolerance. Moreover, EVs play pivotal roles in antimicrobial host defense. They deliver microbial antigens to antigen-presenting cells (APCs), triggering immune responses, or act as decoys to neutralize virulence factors and toxins. This review discusses host and microbial EVs' multifaceted roles in innate and adaptive immunity, highlighting their involvement in immune cell development, antigen presentation, and antimicrobial responses.

Keywords: Ectosomes; OMVs; exosomes; extracellular vesicles; microvesicles.

Figure 1.. Role of extracellular vesicles in immunity and host defense.

Eukaryotic and microbial EVs are potent regulators of the innate and adaptive immune responses. Depending on the cargo, EVs can modulate activation states of neutrophils, NK cells, macrophages, DCs, and various subsets of T cells. Infected eukaryotic cells can also shuttle and deliver microbial components to initiate an immune response in uninfected cells. Microbial EVs potently stimulate cytosolic pattern recognition receptors by delivering LPS and other membrane components, DNA, and flagella to host cells. There is also mounting interest in repurposing microbial EVs as vaccine platforms, owing to their intrinsic ability to carry and delivery cargo and adjuvant properties.